| 1. |
- Håkanson, Ulf, et al.
(författare)
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Photon mapping of single quantum dots by scanning tunneling microscopy induced luminescence spectroscopy
- 2002
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Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
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Konferensbidrag (refereegranskat)abstract
- Scanning tunneling microscopy induced luminescence (STML) has been used to investigate individual self-assembled InP quantum dots overgrown with GaInP. We will present results correlating the surface morphology with the optical properties of single dots. In particular, the strain induced energy-shift of the dot emission with increasing cap layer thickness and its relation to the overgrowth will be discussed. Effects of the dots on the properties of the overgrown GaInP will also be treated. STML spectra and monochromatic photon maps are compared with results from photoluminescence and transmission electron microscopy measurements. Furthermore, a comparison with theoretical calculations is made
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| 2. |
- Håkanson, Ulf, et al.
(författare)
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Single InP/GaInP quantum dots studied by scanning tunneling microscopy and scanning tunneling microscopy induced luminescence
- 2002
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:3, s. 494-496
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the optical and structural properties of single, self-assembled InP quantum dots (QDs) overgrown with nominally 5 nm of GaInP, using an ultrahigh-vacuum scanning tunneling microscope (STM) operating at low temperatures. The STM is combined with an optical detection system, which allows us to detect the emission from individual quantum dots with high spatial resolution. We find that the InP QDs act as nucleation points for the GaInP overgrowth, where the strain induced by the overlayer give rise to a QD emission around 1.46 eV. (C) 2002 American Institute of Physics.
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| 3. |
- Håkanson, Ulf, et al.
(författare)
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Ultrahigh vacuum scanning probe investigations of metal induced void formation in SiO2/Si(111))
- 2002
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Ingår i: JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 20:1, s. 226-229
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Konferensbidrag (refereegranskat)abstract
- Using scanning electron microscopy guidance, atomically resolved scanning tunneling microscopy investigations inside openings formed during the decomposition of a thick SiO2 film on a Si(111) surface have been performed. We report, for the first time, the presence of Ni atoms inside self-formed openings. The SiO2 decomposition as a function of annealing temperature and time was studied. By comparing self-formed and lithographically designed openings in the SiO2 layer we have shown that Ni contamination of the SiO2/Si(111) has a profound effect on the formation of self-induced lateral oxide openings. (C) 2002 American Vacuum Society.
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| 4. |
- Johansson, Mikael, et al.
(författare)
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Correlation between overgrowth morphology and optical properties of single self-assembled InP quantum dots
- 2003
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 68:12
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the early stages of GaInP overgrowth on InP quantum dots (QD's) experimentally and theoretically. A direct correlation between the surface morphology and the optical properties of individual InP QD's is made using scanning tunneling microscopy (STM) and scanning tunneling luminescence. The geometric structure of the islands is further investigated using cross-sectional transmission electron microscopy (TEM). The overgrowth occurs in three stages; initially the InP QD's act as seeding points for the overgrowth, where the GaInP grows laterally from the side facets of the QD. The growth occurs preferentially in the [110] direction and elongated GaInP/InP islands are formed. As the overgrowth continues the islands increase laterally in size and GaInP also starts to grow between the islands, but not covering the top of the InP QD's. The growth of GaInP on top of the QD's commences once the islands have begun to coalesce. Using a model based on the STM and TEM results the electronic structures of the QD's have been calculated by eight-band k.p theory. The calculations are in good agreement with the experimental results. Our findings unravel the details of the strain induced energy shift of the QD luminescence previously reported [Pistol , Appl. Phys. Lett. 67, 1438 (1995)].
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| 5. |
- Håkanson, Ulf, et al.
(författare)
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Nano-aperture fabrication for single quantum dot spectroscopy
- 2003
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 14:6, s. 675-679
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple and controllable method for fabricating nano-apertures in a metal film using polystyrene nano-spheres as masks during the metal evaporation. We show how the processing conditions used during deposition of the spheres such as spin velocity, nano-sphere concentration and a reduction of the surface tension interplay and control the distribution of spheres. The fabrication method is ideal for luminescence studies by isolating individual nanometre-sized objects, which is exemplified by photoluminescence spectroscopy of single self-assembled Stranski-Krastanow quantum dots.
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| 6. |
- ZhiQiang, Guan, et al.
(författare)
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Surface-enhanced Raman scattering on dual-layer metallic grating structures
- 2010
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Ingår i: Chinese Science Bulletin. - : Springer Science and Business Media LLC. - 1001-6538 .- 1861-9541. ; 55:24, s. 2643-2648
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Tidskriftsartikel (refereegranskat)abstract
- Dual-layer Metallic grating (DMG) structures as surface-enhanced Raman scattering (SERS) substrates are studied using benzenethiol as the probe analyte. The DMG structure consists of a SiO2 grating and 100-nm-thick gold coating layers. An enhancement factor of 10(5) is achieved by optimizing the SiO2 grating height within the range from 165 to 550 nm. The enhancement factor dependence on the SiO2 grating height is due to the surface plasmon excitation, which is dependent on the polarization of the incident light, and confirmed by finite difference time domain simulations. This study demonstrates the advantages of high uniformity, reproducibility and sensitivity in the DMG structures for SERS applications.
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